<div class="note">
Default pointer values given to duk_opt_xxx() and duk_get_xxx_default() are
not tracked by Duktape, e.g. duk_opt_string() does not make a copy of the
default string argument.  The caller is responsible for ensuring that the
default pointer remains valid for its intended use.  For example,
duk_opt_string(ctx, 3, "localhost") works fine because a string constant is
always valid, but if the argument is a libc allocated string, caller must
ensure the pointer returned from duk_opt_string() is not used beyond the
lifetime of the libc allocated string.
</div>
